1. Field of the Invention
The present invention relates to a method for fabricating a pattern, and more particularly, to a method for fabricating a pattern having equal width and spacing.
2. Description of Related Art
As the level of integration of integrated circuits (IC) continues to increase, the size of each semiconductor device and the distance between the semiconductor devices in integrated circuits must be reduced. In other words, to increase the packaging density of devices and the integration of integrated circuits, the pitch of the pattern, that is the sum of the width and spacing of the pattern, must be reduced. Generally, the miniaturization of pattern pitch in IC fabrication is mostly done by lithography having high resolution. In other words, the width and spacing are determined by the photoresist layer that has been exposed and developed.
Using a light source with a shorter wavelength is one way to improve the resolution. Currently, the 193 nm (ArF) lithography is the shortest wavelength of light that has been developed and a more advanced lithography fabrication is under development. However, there are limiting factors in 193 nm lithography, including the development for the fabrication of photomasks and photoresist materials. As a result, 193 nm lithography encounters problems such as low resolution and poor quality of photoresist pattern. Moreover, 193 nm lithography is limited by optics per se. Hence, the technology is relatively complex and the manufacturing cost is relatively high. Therefore, 248 nm (KrF) lithography is more conunonly used by the industry. Nonetheless, 248 nm lithography, combined with other resolution enhancement techniques, cannot be extended to below 100 nm width. Furthermore, the tools and materials used in today's improved lithographic system required by the lithographic fabrication add on to the manufacturing costs. Consequently, as the semiconductor fabrication technique is required to increase of the integration of device, the industry aims to resolve the aforementioned issues encountered in the fabrication process.